The investigation started with a call about shots fired on I-4.
Florida Highway Patrol troopers responded at around 3:30 p.m. to the eastbound lanes near McIntosh Road.
They found a 17-year-old boy in a vehicle – unresponsive. He was rushed to Baptist Hospital in Plant City but later died.
Hillsborough County Sheriff’s Office deputies are now investigating the shooting as a homicide. Detectives say they searched a two-mile stretch of the highway for evidence, but the shooter has not been caught.
They say the shooting does not appear to be random.
Deputies are looking for a tan Ford Taurus from the 1990s and offering a $5,000 reward for information.
Tips can be left anonymously by calling Crime Stoppers at 1-800-873-TIPS (8477).